104 C. Schuclwrt — Problem of Continental Fracturing 



approaches a state of isostatic equilibrium," therefore this 

 balance is demonstrated everywhere over the earth's surface. 

 It is Hue that he writes "perhaps everywhere" but his argu- 

 ment is positive and unqualified when applied to Gondwana. 

 We must, therefore ask, What do Ave know about the detailed 

 isostasy of the oceanic areas ? The answer must be that in a 

 broad way we know much, and that the oceanic bottoms are on 

 the average of denser rock than the lands. However, it is not 

 only a question of average densities but the greater one as to 

 what we know of the specific gravity of the entire area of any 

 ocean bottom. The answer in this case must be "Very little 

 indeed," because it is well known to geodesists that no knowl- 

 edge is more desirable than a complete survey of the oceanic 

 areas as to their detailed specific gravities and bottom relief. 

 The writer therefore concludes that it is not "hard to imagine 

 a mechanism that could do the work" because it is the same 

 mechanism that in Mesozoic time made the present channel of 

 Mozambique which separates Madagascar from Africa — a 

 sunken block now a water-way from 240 to 600 miles wide 

 and from 5,000 to 10,000 feet deep. 



As for the ancient life found living and fossil in the conti- 

 nents of the southern hemisphere, and especially with regard 

 to the distribution of the Permian Glossopteris flora, those who 

 hold to the complete permanency of continents and oceans say 

 that we are still too ignorant of the world's organisms and their 

 histories to conclude from them that their asylums (Australia, 

 India, Africa, South America, Antarctica) were formerly con- 

 nected one with another; or they hold that the organisms 

 reached these places by accidental dispersal through the air 

 or by being rafted across the intervening water areas. This 

 conflict of views marks one of the greatest outstanding problems 

 of geology and paleontology. The writer, however, is over- 

 whelmed by the facts revealed in the geographic distribution 

 of the ancient land floras and faunas and the marine life, and 

 is compelled to dissent from the rigid view of the permanency 

 of continents. 



Conclusions. — To sum up, we may say that the bottom of the 

 Pacific Ocean in the region of greater Australasia seemingly 

 became more and more mobile with the Lower Carboniferous 

 and especially during the Jurassic and Cretaceous. During this 

 very long time the eastern half of the Australasian continent, 

 a land about 1,800 miles east and west and 2,200 miles north 

 and south, was folded into a series of parallel ridges trending 



